There exists a need for dual particulate and gas/vapor removing protection in the personnel safety market. Three types of gas/particulate combination filter assemblies are known.
Of these assemblies, the first 100 (FIG. 5) includes a simple sheet of particulate filter material or media 102 held between a gas/vapor cartridge 104 and a hard plastic cover 106 joined to the cartridge. Sealing of the media 102 is sometimes imperfect between the cover 106 and the cartridge 104. Similarly, the cover 106 occasionally does not fit properly onto the cartridge 104, especially where the media 102 is not placed with care.
In another configuration 200 (FIG. 6), a particulate cartridge 102 is simply joined permanently to the face of a gas/vapor cartridge 104, in effect "piggy-backing" the two together as a single unit 200 with two stages of filtration. However, the two cartridges may not have the same useful lives under differing environmental conditions.
It is also known (FIG. 7) to use a connecting adapter to join a particulate filter to a gas/vapor cartridge. In one example, a hard plastic adapter 300 is shaped to fit onto a gas/vapor cartridge 302 with a soft, flexible gasket 304 interface to provide an airtight seal between the cartridge 302 and the adapter. The adapter 300 is provided with a bayonet connector 306 for mating with a similar connector 308 on a particulate filter 308. Another soft, flexible gasket 310 is required to ensure that an airtight seal is accomplished between the adapter 300 and the particulate filter 308. With wear, the seals 304, 310 must be replaced to retain assurance of an effective seal. Also, worn seals 304, 310 become more subject to damage and/or loss. Use of the adapter 300 without seals 304 or 310 may be harmful or even hazardous. It is believed that such adapters are available from 3M, St. Paul, Minn., under manufacturer's part number 502.